1. Field of the Invention
The invention relates to slide fasteners and particularly to slide fasteners having coupling elements formed from continuous filamentary materials secured to the adjoining edges of an opening for opening and closing the opening.
2. Description of the Prior Art
Prior art slide fasteners, such as illustrated in U.S. Pat. Nos. 1,581,751, 3,283,379, 3,290,747, 3,359,604, 3,665,561, 3,750,260, 3,783,476, and 3,789,465, employ coupling elements formed from continuous filaments with leg portions of the coupling elements secured by stitching threads to adjacent edges of respective carrier tapes; such slide fasteners depend upon the carrier tapes to provide longitudinal and transverse dimensional stability to the filamentary coupling element. Thus, these prior art slide fasteners employed relatively heavy or strong and dimensionally stable tapes for supporting the filamentary interlocking elements. In certain types of garments, such as those formed from relatively sheer materials, knitted materials, or the like, the relatively heavy tapes or prior art slide fastener degrade the appearance of the garments or their flexibility. Some of the prior art slide fasteners employed filler cords or elongated members extending between leg portions longitudinally in the filamentary coupling elements to aid in the attachment of the coupling elements by stitched or woven threads to the edges of the tapes; such slide fasteners still depending primarily upon the strength and rigidity of the carrier tape for longitudinal and transverse dimensional stability of the slide fastener stringers.
Great Britain Patent Specification No. 1,305,790 discloses a meander shape stringer having alternate short and long loops with a strip welded between the legs of the longer loops and the interconnecting curves of the shorter loops, the welded arrangement ensuring spacing between coupling element; coupling elements having their leg portions all welded together are generally deficient in flexibility, ease of operation, reliability, economy of manufacture, or the like.